kconfig: qconf: remove qInfo() to get back Qt4 support

qconf is supposed to work with Qt4 and Qt5, but since commit
c4f7398b ("kconfig: qconf: make debug links work again"),
building with Qt4 fails as follows:

  HOSTCXX scripts/kconfig/qconf.o
scripts/kconfig/qconf.cc: In member function ‘void ConfigInfoView::clicked(const QUrl&)’:
scripts/kconfig/qconf.cc:1241:3: error: ‘qInfo’ was not declared in this scope; did you mean ‘setInfo’?
 1241 |   qInfo() << "Clicked link is empty";
      |   ^~~~~
      |   setInfo
scripts/kconfig/qconf.cc:1254:3: error: ‘qInfo’ was not declared in this scope; did you mean ‘setInfo’?
 1254 |   qInfo() << "Clicked symbol is invalid:" << data;
      |   ^~~~~
      |   setInfo
make[1]: *** [scripts/Makefile.host:129: scripts/kconfig/qconf.o] Error 1
make: *** [Makefile:606: xconfig] Error 2

qInfo() does not exist in Qt4. In my understanding, these call-sites
should be unreachable. Perhaps, qWarning(), assertion, or something
is better, but qInfo() is not the right one to use here, I think.

Fixes: c4f7398b ("kconfig: qconf: make debug links work again")
Reported-by: Ronald Warsow <rwarsow@gmx.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>